Generation of coherent LO phonons by nonlinearly induced longitudinal light

Summary form only given. If resonantly excited the effect of the longitudinal phonon mode is dominant resulting in an effective three-wave interaction. Photons are down converted between the optical waves while creating a coherent phonon emission via difference frequency mixing. If a phonon background is present and a single optical pulse is injected, a new down-shifted wave is generated. In any case a mutual locking of the two optical pulses can be observed although their group velocities are different. In the coherent case a subsequent up and down conversion occurs, where an equilibrium state of the field distribution is readily obtained for incoherent phonons. In the latter case the resulting rather stable bound state. The created pulses can be used to detect the density and spectral properties of the phonon background.